The graph shows our predictions of the Dst index (blue
line) over the past week, compared with the quick-look Dst measurements
subsequently recorded by the World Data Centre for Geomagnetism (WDC-C2), Kyoto, Japan
(black line).
View the equivalent plot for the:

The coloured bar on the right hand side of the graph indicates an activity
level corresponding to the Dst value. Low activity
is defined as Dst > -20 nT, medium activity is
-20 nT > Dst > -50 nT and high activity Dst <
-50 nT.

We define a magnetic storm as
any interval for which Dst is less than -20 nT and during which Dst drops below
-50 nT (into the high activity zone). Thus green indicates no storm, a green - amber sequence may
indicate the start of a storm, but a full green -
amber - red sequence is
needed to identify a storm conclusively.